The present invention relates to local radiocommunication systems.
More particularly, the invention relates to a local radiocommunication system comprising:
at least one central controller,
several bases connected to the controller and controlled by said controller,
and several terminals, each communicating with at least one of the bases, according to a master/slave process where the base plays a role of master and the terminal plays a role of slave at least after setting up a radio link between said base and said terminal, the bases communicating with the terminals according to the same time division multiple access local radiocommunication protocol (for example the BLUETOOTH protocol or the DECT protocol), said protocol providing, for each base, successive time slots during which either an uplink information packet sent by a terminal to said base or a downlink information packet sent by said base to said terminal are transmitted, and said base being adapted to determine in advance and impose planned transmissions between said base and said terminal, said planned transmissions comprising planned transmissions of downlink information and planned slots of uplink information, where the terminal is authorized to transmit an uplink information packet to the base, and at least some of said bases being susceptible to reciprocal interference, preventing the reception by one of said bases of an uplink information packet when another of said bases is transmitting a downlink information packet.
Document WO-A-00/69186 describes an example of a local radiocommunication system of this type.
In a local radiocommunication system of this type, there is, however, a risk of interference between the transmission of an uplink information packet from a terminal to a base and the transmission of a downlink information packet from a different base to a terminal (at the same frequency or at an adjacent frequency).
Such interferences must be avoided since they render the uplink information packets “inaudible” to the bases, due to the fact that the uplink information radio signals are generally received by a base with a power which is substantially weaker than the power of the downlink information signals transmitted by a different base: the uplink information packets thus lost must subsequently be retransmitted, thereby reducing the effective throughput of the radiocommunication system.
The object of the present invention is, in particular, to eliminate this disadvantage by reducing the probability of interference between uplink information packets and downlink information packets.
For this purpose, according to the invention, a radiocommunication system of the type concerned is characterized in that the different bases are adapted to transmit to the controller, in real time, at least chronological information relating to transmissions planned by said bases, and in that said controller is adapted to determine whether there is a risk of interferences occurring between said planned transmissions, and to impose on the bases a chronology of said planned transmissions which enables at least some of said interferences to be avoided.
Thanks to these measures, the controller makes it possible for the majority of interferences between uplink and downlink connections to be foreseen and avoided, taking account of the fact that the large majority of downlink communications are planned in advance by the bases, and that the large majority of uplink communications are authorized by the bases.